The Big Sleep, like most of Chandler's novels, was written by what he called "cannibalizing" his short stories. Chandler would take stories he had already published in the pulp magazine Black Mask and rework them into a coherent story. For the The Big Sleep, the two main stories that formed the core of the novel were "Killer in the Rain" (published in 1935) and "The Curtain" (published in 1936). Although the stories were independent and shared no characters, they had some similarities that made it logical to combine them. In both stories there is a powerful father, who is distressed by his wayward daughter. Chandler merged the two fathers into a new character and did the same for the two daughters, resulting in General Sternwood and his wild daughter Carmen. Chandler also borrowed small parts of two other stories: "Finger Man" and "Mandarin's Jade".
As might be expected, all this cannibalizing—especially in a time when cutting and pasting was done by literally cutting and pasting paper—sometimes resulted in a plot that had a few loose ends; in the case of The Big Sleep, there is the famous question of who killed the chauffeur. When Howard Hawks made his film of the novel, the writing team were perplexed as to the answer. Hawks contacted Chandler to inquire and Chandler replied he had no idea. This exemplifies a difference between Chandler's style of crime fiction and previous authors. For Chandler the plot was almost secondary; what really mattered was the atmosphere and the characters. An ending that answered all the questions and neatly wrapped up every plot thread, was less important to Chandler than having interesting characters, who behave in believable ways.
When Chandler merged his stories into a novel, he spent more effort on expanding descriptions of people, places, and Marlowe's thinking, than getting every detail of the plot perfectly consistent. In "The Curtain", the description of Mrs. O'Mara's room is just enough to establish the setting: "This room had a white carpet from wall to wall. Ivory drapes of immense height lay tumbled casually on the white carpet inside the many windows. The windows stared towards the dark foot-hills, and the air beyond the glass was dark too. It hadn't started to rain yet, there was a feeling of pressure in the atmosphere." In The Big Sleep, Chandler expanded this description of the room and used new detail (e.g., the contrast of white and "bled out", the coming rain) to foreshadow the fact that Mrs. Regan (who was Mrs. O'Mara in the original story) is covering up the murder of her husband by her sister and that the coming rain storm will bring more deaths: "The room was too big, the ceiling was too high, the doors were too tall, and the white carpet that went from wall to wall looked like a fresh fall of snow at Lake Arrowhead. There were full-length mirrors and crystal doodads all over the place. The ivory furniture had chromium on it, and the enormous ivory drapes lay tumbled on the white carpet a yard from the windows. The white made the ivory look dirty and the ivory made the white look bled out. The windows stared towards the darkening foothills. It was going to rain soon. There was pressure in the air already."